The present invention generally relates to ways of treating health related disorders. More particularly, the invention provides a system and method for treating certain types of breathing problems occurring in a mammal during sleep or other states of diminished consciousness. Merely by way of example, the invention is applied using a plurality of oral appliances for stepped treatment of obstructive sleep disordered breathing.
Many dentists employ oral appliances to treat various forms of obstructive sleep disordered breathing (OSDB). In this context, Schmidt-Nowara et al (Sleep. 1995 July; 18(6):501-10.) define “oral appliances” as a generic term of “devices inserted into the mouth in order to modify the position of the mandible, the tongue, and other structures in the upper airway for the purpose of relieving snoring or sleep apnea.” Lowe (Pages 929-939 in: M H Kryger et al (eds). Principles and Practice of Sleep Medicine. 3rd edition. Philadelphia: W.B. Saunders Company, 2000.) (Oral Maxillofacial Surg Clin N America. 2002; 14:305-317.) describes several commercially available oral appliances. These devices are generally worn by patients during sleep, and removed after awakening.
As implied by its name, obstructive sleep disordered breathing is generally associated with an obstruction to respiratory airflow during sleep. Kuna and Remmers (Pages 840-858 in: M H Kryger et al (eds). Principles and Practice of Sleep Medicine. 3rd edition. Philadelphia: W.B. Saunders Company, 2000.) declare “The site of upper airway obstruction lies in the pharynx,” which is a component of the upper airway. Ferguson (Clin Chest Medicine. 2003; 24:355-364.) states that “Oral appliances may improve upper airway patency by enlarging the upper airway or decreasing upper airway collapsibility.” She further notes that that simple active anterior movement of the tongue or mandible can increase cross-sectional airway size. Lowe (Oral Maxillofacial Surg Clin N America. 2002; 14:305-317.) notes that the tongue is attached to the mandible and that devices that move the mandible anteriorly generally move the tongue anteriorly as well. He discusses the therapeutic mechanism(s) of oral appliances: “Oral appliances . . . appear to work because of an increase in airway space, the provision of a stable anterior position of the mandible, advancement of the tongue or soft palate, and possibly by a change in genioglossus muscle activity.” Guilleminault and Quo (Dent Clin North Am. 2001 October; 45(4):643-656.) note that different mechanisms may contribute in children: mandibular forward-repositioning functional appliances “achieve results on the combined premise of growth adaptation and tooth movement.”
Ferguson (Clin Chest Medicine. 2003; 24:355-364.) reviews several studies of the effectiveness of oral appliance therapy for OSDB and concludes they are effective in some patients with OSDB, particularly those with less severe OSA or simple snoring. She remarks that oral appliances are an appealing form of therapy for OSDB “because they are simple to use, reversible, and portable and generally have a low complication rate.”
According to Ferguson (Clin Chest Medicine. 2003; 24:355-364.) the two major types of oral appliances used in treating OSDB are tongue repositioning devices and mandibular repositioning appliances (MRAs). Schmidt-Nowara et al (supra.) state that “all oral appliances produce downward rotation of the mandible to varying extent; many also advance the mandible by design.”
Ivanhoe and Attanasio (Dent Clin North Am. 2001 October; 45 (4):733-58.) report evidence that a compromised airway, as may be encountered in OSDB, “can be almost completely restored” by moving the mandible forward to 100% of its protrusive capability. On the other hand, they also report that positioning the mandible at 100% of its protrusive capability is “not an acceptable position for most patients because it is generally uncomfortable to maintain through the entire course of sleeping.”
From this, one might conclude, as a rule of thumb, the greater the degree of mandibular advancement conferred by an MRA, the more effective it is in treating OSDB, all other factors being equal. As a further rule of thumb, however, the greater the degree of mandibular advancement, the greater the likelihood the patient will experience discomfort, all other factors being equal.
According to Lowe (Pages 929-939 in: M H Kryger et al (eds). Principles and Practice of Sleep Medicine. 3rd edition. Philadelphia: W.B. Saunders Company, 2000.), “dentists early on realized that determining the correct jaw position was the most difficult step in using oral appliances successfully” in treating OSDB. In many cases there is a tradeoff between efficacy and comfort.
To ease the task of determining the correct jaw position, the dentist may employ an adjustable MRA, as distinguished from a non-adjustable MRA. According to Schmidt-Nowara et al (Sleep. 1995 July; 18(6):501-10.), adjustable MRAs allow readjustment of the mandibular position after initial construction of the device; for non-adjustable MRAs, such readjustments would require refabrication of the entire device. Cartwright (Sleep Med Rev. 2001 February; 5(1):25-32.), for example, views the lack of adjustability in an oral appliance as disadvantageous.
According to one method of using an adjustable MRA, anterior displacement of the mandible is gradually increased (via the MRA) over time, until the desired therapeutic effect is attained or until patient discomfort supervenes. Exemplary adjustment rates include 0.25 mm/night (Ivanhoe and Attanasio. Dent Clin North Am. 2001 October; 45(4):733-58.), 0.5 mm/week (Lowe. Oral Maxillofacial Surg Clin N America. 2002; 14:305-317.), and 1.5 mm increments (Lowe 2002 supra.). Ivanhoe and Attanasio (supra.) report that, with either a fixed or adjustable MRA, “the initial position of the mandible is generally approximately 70% to 75% of maximum protrusion relative to maximum retrusion.” After initial fitting, an adjustable MRA may be configured by repeated assessment to yield the best tradeoff between efficacy and comfort, a process sometimes called “titration.”
A variety of mechanisms, e.g. a screw as used in one MRA known as the Klearway device, or a plunger mechanism as used in the Herbst appliance, have been used to confer adjustability on MRAs. Some mechanisms allow the patient to make adjustments to the MRA. Other mechanisms are less likely to be configured by the patient, and are more commonly adjusted by the dentist. In either case, problems may be associated with adjustable appliances.
For MRAs that are adjusted by the dentist, each adjustment will normally require the patient to bring the MRA to the dentist's office for the adjustment. Such repeated trips may be inconvenient for the patient.
For MRAs that are adjusted by the patient, care must be taken to ensure the instructions to the patient are clear and correctly understood, and that the proper adjustment tools, if any, are available. Oversight by the dentist may also be necessary to detect errors in adjustment by the patient. For example, if the patient turns the screw of the Klearway device in one direction, the effect will be to advance the mandible; if turned in the other direction, the effect will be opposite. Furthermore, a special tool is given to the patient to make adjustments in the Klearway; the patient may lose this tool. Lowe (Oral Maxillofacial Surg Clin N America. 2002; 14:305-317.) cautions that disengaging the tool from the Klearway at the wrong time may prevent the patient from fully engaging the tool at a later time. Some patients with mental impairment or poor hand-eye skills, perhaps due to poor eyesight or severe arthritis, may be unable to adjust the appliance correctly. Thus, it is reasonable to expect that at least some patients tasked to adjust a MRA will have to be seen in a dentist's office at some point during the titration process.
Some adjustable appliances have the potential disadvantage of requiring concentration to make adjustments. For example, an appliance requiring the turn of a screw cannot be adjusted without attention to the screw, the method of turning the screw, and so forth. This may limit the situations in which the appliance may be adjusted, and increase the difficulty that certain classes of patients, may have with the appliance.
Some patients may have to be seen in a dentist's office at the conclusion of the titration process, even when the adjustments have gone smoothly. Advice on the Klearway device, for example, recommends that the dentist “lock in” the configuration of the device once it has been properly adjusted, as follows (Lowe. Oral Maxillofacial Surg Clin N America. 2002; 14:305-317.): “The expansion screw should be tied off with stainless steel ligature wire or filled in with cold cure acrylic to prevent any further movement of the screw.” An appliance thus locked-in may no longer be adjustable. Non-adjustability may become undesirable later, as Ivanhoe and Attanasio (Dent Clin North Am. 2001 October; 45 (4):733-58.) caution that “titration may become necessary again at some future time if sleep disorder symptoms recur or tooth or temporomandibular joint sensitivity appears.”
Another potential disadvantage of adjustable MRAs is their mechanical complexity. Mechanical complexity may cause increased manufacturing expense and/or increased failure rates. The adjustment mechanism in the Klearway device, for example, appears to be a component that must itself be manufactured separately and integrated into the rest of the device. It is also a component that may fail. In 2001 Cartwright (Sleep Med Rev. 2001 February; 5 (1):25-32.) quoted a typical cost of $40-400 for certain types of non-adjustable oral appliances used to treat OSDB, and compared this to a typical $800-2000 cost for an adjustable MRA.
Thus, it is seen that MRAs may have a variety of potential shortcomings, including being non-adjustable, inconvenient, difficult or confusing for patients to adjust, relatively failure-prone, and expensive. Adjustable appliances rendered non-adjustable at the completion of titration may not be able to be used if re-titration becomes necessary or desirable.
From the above, it is desirable to have improved techniques for treating health related disorders.